Unidirectional Single-File Transport of Full-Length Proteins Through a Nanopore

Nanopore technology offers long, accurate sequencing of an DNA or RNA strand via enzymatic ratcheting of the strand through a nanopore in single nucleotide steps, producing stepwise modulations of the nanopore ion current. In contrast to nucleic acids, their daughter molecules, proteins, have neutral peptide backbones and side chains of varying charges. Further, proteins have stable secondary and higher order structures that obstruct protein linearization required for single file nanopore transport. Here, we describe a general approach for realizing unidirectional transport of proteins through a nanopore that neither requires the protein to be uniformly charged nor a pull from a biological enzyme. At high concentrations of guanidinium chloride, we find fulllength proteins to translocate unidirectionally through an a-hemolysin nanopore in a polymer-based membrane, provided that one of the protein ends is decorated with a short anionic peptide. Molecular dynamics simulations show that such surprisingly steady protein transport is driven by a giant electro-osmotic effect caused by binding of guanidinium cations to the inner surface of the nanopore. We show that ionic current signals produced by protein passage can be used to distinguish two biological proteins and the global orientation of the same protein (N-to-C vs. C-to-N terminus) during the nanopore transport. With the average transport rate of one amino acid per 10 μs, our method may enable direct enzyme-free protein fingerprinting or perhaps even sequencing when combined with a high-speed nanopore reader instrument.

Salt stress slows down dynamic photosynthesis mainly through osmotic effects on dynamic stomatal behavior

Salt stress affects stomatal behavior and photosynthesis, by a combination of osmotic and ionic components, but it is unknown how these components affect photosynthesis dynamics under fluctuating light. Tomato (Solanum lycopersicum) plants were grown using a reference nutrient solution (Control, EC: 2.3 dS m-1), the reference containing extra macronutrients (only osmotic effect; EC: 12.6 dS m-1), or the reference containing an additional 100 mM NaCl (osmotic and ionic effects; EC: 12.8 dS m-1). Steady-state and dynamic photosynthesis along with leaf biochemistry were characterized throughout leaf development. Osmotic effects resulted in increased leaf chlorophyll content per unit leaf area, induced stomatal closure along with rapid stomatal responses to changes in light intensity, and limited dynamic but not steady-state photosynthesis. Ionic effects were barely observed in plant growth and dynamic photosynthesis, but led to a reduction in leaf chlorophyll content and photosynthetic capacity in old leaves. Steady-state and dynamic photosynthesis traits decreased with leaf age, due to increases in stomatal and non-stomatal limitations. With increasing leaf age, rates of light-triggered stomatal movement decreased across treatments, which is more strongly for stomatal opening rather than closure. We conclude that osmotic effect strongly impacts dynamic stomatal and photosynthetic behavior under salt stress.

Physiological Indicators in Two Lettuce Cultivars Under Saline Stress

Lettuce (Lactuca sativa L.) is considered as the main leafy vegetable in Brazil. In the last decades, there had been many changes in the predominant varietal types in the country, however, issues regarding the use of saline water inhibit the growth by the osmotic effect. The aim of this study is avaliate the effect of water salinity on physiological in lettuce cultivars. The experiment was carried out at the Alagoas Federal University, Arapiraca Campus, in a completely randomized design and with a 5 × 2 factorial scheme, with six replications. Five treatments of water salinity levels were analyzed (ECw: 0.14, 1.54, 2.94, 4.34, and 5.74 dS m-1 at 25 °C) in two types of lettuce crops (Saia Véia and Vitoria Verdinha). Stomatal conductance, net photosynthesis, transpiration rate, water use efficiency, leaf temperature, and green index were assessed at 10, 20, and 30 days after the application of the treatments. The saline stress caused by the increase in saline concentrations decreased the photosynthesis and transpiration rates, which were associated with the reduction of stomatal conductance in both cultivars. Nevertheless, Saia Véia cultivar was higher tolerance in all tested saline levels compared to Vitória Verdinha. The green index for Vitoria Verdinha was seven times higher when compared to Saia Véia from the lowest to the highest saline levels. The cultivars differ in salt sensitivity, which could be useful for producers to choose the cultivar that is most adapted to the region and breeders regarding improvement prospects for adaptation of the lettuce under saline stress. In addition to osmotic stress, which is the first to happen, there are others.

Seasonal changes in carbohydrates and water content predict dynamics of frost hardiness in various temperate tree species

Predicting tree frost tolerance is critical to select adapted species according to both the current and predicted future climate. The relative change in water to carbohydrate ratio is a relevant trait to predict frost acclimation in branches from many tree species. The objective of this study is to demonstrate the interspecific genericity of this approach across nine tree species. In the studied angiosperm species, frost hardiness dynamics were best correlated to a decrease in water content at the early stage of acclimation (summer and early autumn). Subsequently, frost hardiness dynamics were more tightly correlated to soluble carbohydrate contents until spring growth resumption. Based on different model formalisms, we predicted frost hardiness at different clade levels (angiosperms, family, genus and species) with high to moderate accuracy (1.5–6.0°C RMSE) and robustness (2.8–6.1°C RMSEP). The TOT model, taking all soluble carbohydrate and polyols into account, was more effective and adapted for large scale studies aiming to explore frost hardiness across a wide range of species. The ISC model taking the individual contribution of each soluble carbohydrate molecule into account was more efficient at finer scale such as family or species. The ISC model performance also suggests that the role of solutes cannot be reduced to a 'bulk' osmotic effect as could be computed if all of them were located in a single, common, compartment. This study provides sets of parameters to predict frost hardiness in a wide range of species, and clues in targeting specific carbohydrate molecules to improve frost hardiness.

Decreased Levels of Thioredoxin o1 Influences Stomatal Development and Aperture but Not Photosynthesis under Non-Stress and Saline Conditions

Salinity has a negative impact on plant growth, with photosynthesis being downregulated partially due to osmotic effect and enhanced cellular oxidation. Redox signaling contributes to the plant response playing thioredoxins (TRXs) a central role. In this work we explore the potential contribution of Arabidopsis TRXo1 to the photosynthetic response under salinity analyzing Arabidopsis wild-type (WT) and two Attrxo1 mutant lines in their growth under short photoperiod and higher light intensity than previous reported works. Stomatal development and apertures and the antioxidant, hormonal and metabolic acclimation are also analyzed. In control conditions mutant plants displayed less and larger developed stomata and higher pore size which could underlie their higher stomatal conductance, without being affected in other photosynthetic parameters. Under salinity, all genotypes displayed a general decrease in photosynthesis and the oxidative status in the Attrxo1 mutant lines was altered, with higher levels of H2O2 and NO but also higher ascorbate/glutathione (ASC/GSH) redox states than WT plants. Finally, sugar changes and increases in abscisic acid (ABA) and NO may be involved in the observed higher stomatal response of the TRXo1-altered plants. Therefore, the lack of AtTRXo1 affected stomata development and opening and the mutants modulate their antioxidant, metabolic and hormonal responses to optimize their adaptation to salinity.

Use of Mannitol and Saline Solution in the management of ICP in patients with Traumatic Brain Injury: Evidence of superiority?

Background: Mannitol (MT) and Hypertonic Saline Solution (HSS) exert an osmotic effect by lowering Intracranial Pressure (ICP) in patients with Traumatic Brain Injury (TBI), but there are doubts as to which is more efficient. Objective: Analyze the use of MT and HSS in the management of ICP in patients suffering from TBI. Design and Settings: This is a literature review, produced by medical students from Bahia, Brazil. Methods: The evaluated studies were obtained in PubMed, with MeSH terms, published since 1988. The studies that did not correspond with the purpose of this review were excluded. Results: 34 of the 114 articles found, were selected. Observational and laboratory studies have shown an advantage in the use of SSH to reduce ICP and a longer duration of the effect in relation to MT. However, clinical trials and meta-analyzes do not show significant differences in relation to MT and SSH for reducing ICP, however they describe a slight preference for the use of SSH. As for side effects, MT mainly causes hemodynamic changes such as hypotension and SSH causes a significant increase in serum sodium concentration. Conclusion: Although there are benefits to both the use of TM and SSH, there is a preference to use SSH for the management of ICP in patients with TBI. The studies were not enough to show superiority in relation to these solutions and new Clinical Trials must be carried out.

International Medical Graduates - Asset or Liability?

One of the gains of globalisation is its osmotic effect of equalisation motivating all the countries to reach their potential. Human resource especially, medical manpower, determines the health of the nation. Developing countries are becoming increasingly aware, of using their scarce resources to train a doctor, only to lose it to the Western world. The article highlights the exploitation, and possible wastage of highly qualified medical workforce who, are accommodated to suit the needs of the host country irrespective of their previous qualifications and experience. The article also makes suggestions to recover and retain the talents of the country.

INNOVATION OF THE USE OF HONEY AS A TOPICAL MEDICINE TO THE THERAPY OF ABDOMEN'S INCISION POST-CAESAR

Honey has long been used as food and medicine. One of the many researched benefits of honey is that it speeds up wound healing. The Koran and the hadiths clearly state that there is healing in honey. Along with advances in technology, cesarean delivery is increasingly being performed to help facilitate labor under various indications. However, cesarean delivery can limit the mother's activities in the care of herself and her child. On the other hand, cesarean delivery also often causes obstetric complications such as puerperal infection, endometritis, wound complications, and surgical healing complications. It will increase the cost of cesarean delivery. The authors reviewed the data regarding the effectiveness of honey in the therapy of post-cesarean delivery abdominal incisions. The data show that the antibacterial, anti-inflammatory, and antioxidant characteristics of honey can significantly affect the therapy of cesarean delivery incisions. The combination of the osmotic effect and hydrogen peroxide activity in honey can inhibit bacterial growth, reduce edema, exudate, and pain due to inflammatory processes. Besides, honey has the effect of protecting antioxidant enzymes from free radicals and reducing oxidative stress to reduce cell damage. Honey can also stimulate angiogenesis, the proliferation of fibroblasts and epithelial cells, and granulation, helping speed up the healing process. This paper discusses honey's mechanism in accelerating wound healing and its effect in preventing wound infection from improving the quality of health and the relationship between mother and child after cesarean delivery.

Osmo-inelastic response of the intervertebral disc annulus fibrosus tissue

The aim of this article is to provide some insights on the osmo-inelastic response under stretching of annulus fibrosus of the intervertebral disc. Circumferentially oriented specimens of square cross section, extracted from different regions of bovine cervical discs (ventral-lateral and dorsal-lateral), are tested under different strain-rates and saline concentrations within normal range of strains. An accurate optical strain measuring technique, based upon digital image correlation, is used in order to determine the full-field displacements in the lamellae and fibers planes of the layered soft tissue. Annulus stress–stretch relationships are measured along with full-field transversal strains in the two planes. The mechanical response is found hysteretic, rate-dependent and osmolarity-dependent with a Poisson’s ratio higher than 0.5 in the fibers plane and negative (auxeticity) in the lamellae plane. While the stiffness presents a regional-dependency due to variations in collagen fibers content/orientation, the strain-rate sensitivity of the response is found independent on the region. A significant osmotic effect is found on both the auxetic response in the lamellae plane and the stiffness rate-sensitivity. These local experimental observations will result in more accurate chemo-mechanical modeling of the disc annulus and a clearer multi-scale understanding of the disc intervertebral function.